This invention relates to ultrasonic liquid level sensing systems, and more particularly to an ultrasonic beam shaping device that tailors the shape of a transducer beam emitted toward a target, tailors the shape of the return beam received by the transducer after being reflected from the target, and diverts from the transducer and target, extraneous unusable portions of the emitted and reflected transducer beams.
In one known automated sample analysis system which employs sample tubes in tube racks, a plurality of containers or sample tubes, capped or uncapped, and of different size and shape may be held in the sample tube racks. The sample tube racks are automatically transported from one location to another within the sample analysis system for selected automated processing operations.
As disclosed in U.S. Pat. No. 6,227,053 to Purpura et al, automated processing of sample tubes in sample tube racks is facilitated by developing an ultrasonic profile of the sample tubes. An ultrasonic liquid level sensor provides data relating to the type of sample tubes in the sample tube rack, indicating whether the sample tubes are capped or uncapped, and also provides data relating to the liquid level in the sample tubes, if the tubes are uncapped.
The ultrasonic sensor includes a transducer that is operable as a transmitter and a receiver. For example, the transducer can emit an ultrasonic burst that is transmitted in air toward a target. When the ultrasonic burst strikes the target, a portion of the ultrasonic wave is reflected back toward the transducer. The reflected wave is characterized as an echo or beam and a reflected wave can produce one or more echoes.
When the transducer detects the reflected waves or echoes it functions as a receiver. The time lapse between the emission of an ultrasonic burst and the detection of the echo provides data for determining the type of container that is targeted by the transducer.
It is known that an ultrasonic burst diverges and propagates along its travel path as a cone shaped wave. The diversionary spread of the cone shaped wave can extend relatively far beyond the peripheral extremities of a particular target container, such that the echoes may produce relatively indistinct imaging of the container profile as shown, for example, in FIG. 10. An ultrasonic beam of narrower cone width produces echoes that provide higher resolution profiling and a more distinct imaging of the container profile as shown, for example, in FIGS. 11 and 12.
In order to produce an ultrasonic beam transmission having a narrow cone-width it is usually necessary to provide an ultrasonic crystal having a geometry and size that corresponds to a narrow-cone beam emission. However, ultrasonic beam transmissions that have a narrow-cone beam emission pattern generally have reduced emitted energy and reduced sensing range, which can adversely affect the resolution capability of an ultrasonic sensing system.
It is thus desirable to provide a system and method for high resolution profiling of targets, with an ultrasonic transducer that normally produces a beam of relatively wide cone-width. It is also desirable to provide a system and method for reshaping an ultrasonic beam emitted by an ultrasonic transducer without reducing the emitted energy of the ultrasonic beam and without causing extraneous, unusable portions of the emitted and reflected beams to interfere with a liquid level sensing system